Influence of the number of repellent-treated and untreated food or water containers on intake by the European starling.

The availability of multiple sources of food and drink has a profound influence on choice behavior in rodents. It is not known how other taxa might respond to the same kind of variation in availability. We tested European starlings (Sturnus vulgaris) with various combinations of unadulterated and repellent-treated (0.025% citronellyl acetate) resources. In Experiment 1, birds drank more plain than repellent-treated water than when given (a) 2 bottles of plain water and 2 of repellent-water, or (b) 3 bottles of plain water and 1 of repellent-water. However, they drank more repellent than water when given 3 bottles of repellent-water and 1 of plain water. Thus, the aversion to the repellent became indifference when repellent-water was abundant. In Experiment 2, birds ate more untreated than treated food when given (a) 1 cup of untreated food and 1 cup of treated food or (b) 2 cups of untreated food and 1 of treated food. They ate equal amounts of untreated and treated food when given 1 cup of untreated food and 2 cups of treated food. These results demonstrate the effect of relative availability on choice, and imply that availability should be considered when using repellents.